Getter construction



Feb. 18, 1969 c. w. REASH 3,428,168

GETTER CONSTRUCTION Filed Feb. 2. 1967 Sheet 2 of 2 INVENTOR CLAIR W.REASH BY kw A ATTORNEY United States Patent 3,428,168 GETTERCONSTRUCTION Clair W. Reash, Fairview Park, Ohio, assignor to UnionCarbide Corporation, a corporation of New York Filed Feb. 2, 1967, Ser.No. 613,539 US. Cl. 206-.4 12 Claims Int. Cl. H01j 19/70 ABSTRACT OF THEDISCLOSURE A wide channel ring getter having higher capacity ofvaporizable getter material for use particularly in large colortelevision picture tubes. A reinforcing means can be positioned in thechannel to prevent cracking of the getter material during heating of theassembly flashing of the getter material.

Background 09 the invention This invention relates toan improved getterconstruction and more particularly to an improved channel ring getterfor containing a higher capacity of getter material and for moreeffective flashing of such material.

The use of geter materials in the manufacture of electronic tubes iswell known. A commonly used getter construction consists of a container,such as an annular U- shaped receptacle, with the getter materialpressed into the container. This assembly is mounted in an electrontube, for example, a television picture tube. After the tube isevacuated, the residual gases left in the tube are removed by heatingthe getter container and material therein to a high temperature,suitably by induction heating, whereupon the getter material is flashedor vaporized. The vaporized getter material adsorbs or reacts with theresidual gases and removes them as low vapor pressure solid condensatesand continues to adsorb any further liberated gases throughout the lifeof the tube.

Usually the getter material principally comprises: a mixture or alloy ofmetals such as, for example, barium and aluminum. It is the bariumcomponent of this mixture which provides the reactive material. Theclean up of residual gases in the larger sized television picture tubes,and particularly color tubes, requires a relatively large amount ofactive barium material. For example, color tubes having three electronguns and a metal shadow mask have been found to require a yield of 125to 175 mg. of barium. Since the barium-aluminum powder mixture mighthave contained up to about 50% aluminum, the total amount of getteringpowder mixture in the container before flashing could be from 250 to 350mg. It has further been found desirable to employ exothermic getteringpowders in color television picture tubes. An exothermic getteringpowder can comprise: a bariumaluminum alloy or mixture plus about anequal weight of powdered nickel. The nickel reacts exothermically withthe aluminum upon heating to supply additional heat for evaporating thebarium. This self-generated heat lessens the getter flashing time andthe nickel aluminum residue has been found to be more stable than thealuminum residue of the endothermic type getters.

A typical channel rinlg getter used in color television picture tubesthus may contain 250 mg. of a 50% barium-50% aluminum endothermic alloy.The yield of vaporized barium is normally 125 mg., i.e., 100% of thebarium present in the powder alloy is vaporized. However, if anexothermic powder mixture of the same capacity is to be substituted,then it would be necessary to use at least 500 mg. of the exothermic 25%barium- 25% aluminum-50% nickel powder mixture, assuming "ice a yieldcan be obtained to supply the necessary mg. of barium. It has been foundthat serious yield problems exist when such large amounts of powdermixture are pressed into conventional getter containers such that 100%yields of effective barium vapor are not obtained in the normal flashingtimes.

Additionally it has been found that when such large volumes of gettermaterial are flashed from getter containers, cracking of the materialtakes place with the ejection of solid particles into the tubeenclosure. These ejected particles can cause short circuits andotherwise interfere with the operation of tube components.

It is the primary object of this invention therefore to provide animproved getter assembly.

It is another object of this invention to provide an improved getterassembly having a high capacity and freedom from cracking and ejectionof solid particles.

Other aims and objects of this invention will be apparent from thefollowing description, the appended claims and the attached drawings.

Summary of the invention According to the present invention, an improvedchannel ring getter is provided comprising a substantially U- shapedwide channel ring container having opposing side walls and a bottom wallconnecting said side walls, and getter material packed therein to adepth of from 0.025 to 0.035 inch, and more specifically from 0.028 inchto 0.033 inch. A preferred thickness ordepth of packed getter materialis about 0.030 inch. It has been found that when large amounts of gettermaterial, for example, the 500 mg. exothermic mixture often needed forgettering color television picture tubes, are pressed into conventionalchannel ring getter containers, there is too great a thickness oftgettering material present and high yields of vaporized barium cannotbe achieved in the normal heating times. For example, when. a 25 or 36mm. diameter channel ring is used to hold this much material in theconventional 0.06 inch wide channel, the thickness of pressed powder istoo great. Upon heating, the yield of vaporized barium is less than 100%for the normal 15 to 25 second flashing operation. The getter assemblymust be heated for a longer than usual time to achieve higher yields ofvaporized barium. Extended heating times are undesirable. However, whena wider channel, for example, 0.1 inch between side walls, is used tohold the pressed powder in the indicated ranges of powder thicknesses,the yield of vaporized barium is about 100% of the initial bariumcontent of the powder mixture.

However, when a wider channel, for example, 0.1 inch is used to hold thepressed powder so that the depth of pressed powder is within the rangesspecified herein, there is a tendency for the getter material to crackand for solid particles to be ejected.

In a preferred aspect of the invention, therefore, a getter materialreinforcing member is at least partially buried in the packed gettermaterial to ensure against cracking of said getter material duringheating. This reinforcing member can be an insert such as a metallicwire ring having a diameter about midway between the diameter of theinner and outer walls of the channel. The ring is inserted in thechannel and the powder pressed into the channel over the ring insert.

The drawings In the drawings:

FIGURE 1 is an enlarged plan view of a getter container with aring-shaped wire reinforcing member disposed therein;

FIGURE 2 is a cross-sectional view taken along line 22 of FIGURE 1;

FIGURE 3 is an enlarged plan view of a getter container with an L-shapedreinforcing member disposed therein;

FIGURE 4 is a cross-sectional view taken along line 4-4 of FIGURE 3;

FIGURE 5 is a cross-sectional view of a getter container having areinforcing member integrally formed with the getter container; and

FIGURE 6 is a cross-sectional view of a getter container similar to thatshown in FIGURES 1 and 2, but with a flared side Wall for directing theflashed gases.

Preferred embodiments FIGURE 1 shows a channel ring getter 10 havingside walls 11 and 12 joined by a bottom wall 13 defining a channel space14. The width of the channel can be about 0.1 inch and the containerscan hold about 500 mg. or more of pressed getter material 16. Aspreviously stated the thickness of pressed getter material is maintainedat about 0.030 inch. The diameters of the side walls and channel widthare selected so that the thickness of pressed getter material is withinthe range of about 0.025 to about 0.035 inch, with a range of 0.028 to0.033 being preferred. Thicknesses of getter material less than 0.025inch are diflicult to press into the channel; and thicknesses of gettermaterial over 0.035 inch do not upon flashing, give high yields ofbarium which this invention seeks to achieve.

The reinforcing member comprises a wire ring 17 of about 0.015 to 0.02inch in cross-sectional diameter placed midway in the channel space 14.The ring 17 is shown at the bottom of the channel with the gettermaterial 16 pressed into the channel over the ring. The ring could beelsewhere positioned in the bulk of the pressed getter material, forexample, off the floor 13 of the channel if desired.

The reinforcing member can also have other shapes. For example, thinwalled angular members having a configuration suited for insertion inthe channel and having various types of cross sections are suitable.Flanges and other shapes having, preferably, a horizontal leg and avertical leg can be used. The width of the horizontal leg can beone-half the width of the channel and the diameter of the circle formedby the vertical leg can be equal to the diameter of the mid point of thechannel section. The member is then self-centering with the horizontalleg resting on the bottom of the channel with its edge abutting -a sidewall of the container and with the other leg rising vertically at thecenter of the channel. The vertical leg need not rise above the level ofthe powder when pressed into the channel and, preferably, is buriedbeneath the surface of the pressed powder cake. Other shapes and typesof insertable members can be used for reinforcing the gettering powder.

A flange-shaped form of insert member 18 is shown in FIGURES 3 and 4.This L-shaped member has a horizontal leg 19 and a vertical leg 20. Thehorizontal leg 19 can be of a width equal to one half the width of thechannel space 14 so as to be self-centering. The width of the horizontalleg 19 is about 0.05 inch in this case. The horizontal leg can be formedon either side of the vertical leg and is shown here on the inside. Thevertical leg has a height less than the level of the pressed gettermaterial. These inserts can be dropped into the channel prior to fillingwith powder.

Such insertable reinforcing members generally need not be permanentlyjoined to the container structure. It is not usually necessary to weldor otherwise join the insert member to the walls or floor of thechannel, although this can be done if desired. The pressed getteringpowder will generally hold the insert in place until heating. During andafter flashing, the aluminum or aluminum-nickel residue will furtherhold the insert in place. The insert member can be connected to thechannel member if desired, for example, to hold it in place whilegettering powder is dispensed and stamped into the channel.

The reinforcing member can also be an integral part of the channelcontainer. For example, a section of the channel floor can be crimped toform a thin-edged ridge rising above the floor of the channel. The ridgeneed not rise above the level of the pressed powder. FIGURE 5 shows achannel ring container 21, which is similar to those shown previously,but which has a reinforcing member 22 integrally formed in the channelfloor 23. This member 22 is formed by crimping the floor portion to forma thin edged ridge as shown. The getter material 24 is packed downaround the member 22 which will hold the powder residue in place duringflashing.

Thereinforcing member can be of any type construction and shape providedit prevents the gettering material from cracking during heating andejecting solid particles. While it is not intended to be bound to aparticular mechanism by which cracking of the gettering material isprevented, it is believed that the reinforcing member serves to tie eachsegment of the annular body of gettering material to its neighboringsegments, thereby preventing the movement, cracking or ejection of anyindividual segment. Additionally, the presence of the reinforcing memberabout midway between the side walls of the channel may also serve toprovide support for the gettering material at that otherwiseunsupported, intermediate point and thereby, in effect, reduce theunsupported Width of the getter material to about one half the actualdistance between the channel walls.

The reinforcing member will generally have the same shape as the channelcontainer, i.e., if the channel is ring-shaped then the reinforcingmember will be circular. Other suitable forms of reinforcing members canbe used for various shapes of containers.

Wide channel getter assemblies of the types described above were testedby flashing. The stainless steel channel ring containers had an overalldiameter of about 27 mm. and the channel width was about 0.1 inch. Thefill was about 500 mg. of the nickel-aluminum-barium exothermic materialpreviously described. About 27 of these assemblies, which did not haveany reinforcing members, were flashed by inductive heating underconditions similar to those experienced in a color television picturetube. The yield of flashed barium for a 20 second heating time was inall cases, i.e., a yield of mg. of barium. However, in all cases exceptone, there was cracking of the residue powder.

Getter containers similar to those used above were provided with a wirering insert member of 0.015 to 0.020 inch wire diameter and the sameamount of the above described exothmermic getter material packed intothe channel space over the wire ring. Twenty of these assemblies wereflashed with no cracking of the residue powder occurring in any case andno ejection of solids. The yield of vaporized barium was 100%, i.e., thefull 125 mg. of barium.

Another group of similar getter containers were pro vided with stainlesssteel L-shaped inserts shown in FIG- URES 3 and 4 and described above.One hundred of these assemblies were flashed with no cracking of theresidue powder or ejection of solid particles.

It is to be noted that while the invention here has been described inregard to ring shaped channels, it is not so limited and can be used inother shapes of containers. Additionally, the reinforcing members ofthis invention can be used in channel ring getter containers havingflared side walls which give direction to the flow of vaporizedmaterial. Such containers generally have side walls parallel to eachother and perpendicular to the floor of the channel in the area ofpowder fill with upper portions or one or both side walls flaring in orout at an angle to the vertical axis of the channel to direct the flowof vaporized material radially inward or outward. The reinforcing memberwould be placed in the lower portion of the channel occupied by thepacked getter material. As an example, FIGURE 6 shows a channel ringcontainer 25 having its inner wall 27 flaring outwardly so as topartially cover the getter material 27 which has a reinforcing member 28therein. The term channel ring container as used herein is meant toinclude containers of other than ring shape, for example oval and othershapes whether or not the ends of the channel are joined together.

What is claimed is:

1. In a getter assembly provided with a substantially U-shaped channelring container having opposing side walls and a flat bottom wallconnecting said side walls and forming with said side walls an annularopen-topped channel space, and getter material pressed into the bottomof said channel space formed by said side walls and the flat bottomwall, said getter material comprising at least 25 percent by weightbarium as the active flashing getter material and the balancenon-flashing material which forms a breakable residue in the channelspace after the barium is flashed by heating the assembly, theimprovement for preventing cracking of said getter material residue andthe ejection of cracked particles from the container during heatingcomprising reinforcing means in said channel space at least partiallyburied in said pressed getter material for holding said residuetogether.

2. The getter assembly of claim 1 in which the getter material ispressed into said container to a depth of from 0.025 to 0.035 inch.

3. The getter assembly of claim 1 in which the reinforcing means is ametallic wire ring having a diameter about midway between the diametersof the inner and outer side walls of the channel.

4. The getter assembly of claim 1 in which the reinforcing means is ametallic, shaped ring member having one portion resting on the bottomwall of the channel and another portion rising vertically above thebottom wall of the channel.

5. The getter assembly of claim 1 in which the reinforcing means is anL-shaped flange having a horizontal leg with a width equal to aboutone-half of the channel width and having a vertical leg with a heightless than the depth of the powder packed into the channel.

6. The getter assembly of claim 1 in which the reinforcing means is amember extending completely around the annular packed body of gettermaterial and having the getter material adherently packed around saidmember whereby said member ties each portion of the annular body toadjacent portions and prevents relative movement thereof during heatingto a flashing temperature.

7. The getter assembly of claim 1 in which the getter container andreinforcing means are constructed of stainless steel.

8. The getter assembly of claim 1 in which the upper portion of at leastone of the side walls of the container is flared off at an angle to thevertical axis of the channel to direct the flow of vaporized material atthe same angle.

9. The getter assembly of claim 1 in which the reinforcing means is anintegral formed portion of the bottom wall of the channel, said formedportion rising above the surface of the bottom wall and partitioning atleast a portion of the channel space into two compartments.

10. The getter assembly of claim 1 in which the formed partition extendsto a point below the level of the packed powder.

11. In a getter assembly provided with a substantially U-shaped channelring container having opposing side walls and a bottom wall connectingsaid side walls, an improvement for containing large amounts of gettermaterial in said container and for flashing, upon heating of thecontainer, the full amount of active getter material, said improvementcomprising widely spaced apart side walls with about at least 500 mg. ofexothermic, bariumcontaining getter material pressed into the annularspace formed by said side walls and the bottom wall to a depth of from0.025 to 0.035 inch, and reinforcing means in said annular space atleast partially buried in said pressed getter material.

12. The getter assembly of claim 11 in which the width of the channel isat least 0.1 inch and the depth of the pressed getter material is about0.030 inch.

References Cited UNITED STATES PATENTS 1,957,145 5/ 1934 Loewe 2060.4 X

2,060,861 11/1936 Glans 2060.4

3,225,910 12/1965 Della Porta 2060.4

3,023 ,8 83 3 1962 Meisen 2060.4

3,225,911 12/1965 Della Porta 206-0.4

2,824,640 2/ 1958 Della Porta 206--0.4

JOSEPH R. LECLAIR, Primary Examiner.

I. M. CASKIE, Assistant Examiner.

